The present invention relates to an apparatus for evaluating the grade of rice grains such as brown rice, white rice and unhulled rice grains.
In a country such as Japan, such grains as rice grains are subject of severe and strict examination for grading or classification under the law and regulations concerned. The examiners for evaluating the grade of grains are those who have been highly trained to be able to make correct decisions for grades. However, it cannot be guaranteed that such examiners do make correct decisions at all times because the methods of examination normally available are for them to grade grains by the eye only.
The disclosure relating to an apparatus for evaluating the quality or grade of brown rice grains is found, for example, in Japanese Patent Application Kokai No. 125664/1981 and methods of evaluating the same, for example, in Japanese Patent Application Kokai No. 153249/1982 and Japanese Patent Application Kokai No. 150141/1987.
The apparatus disclosed in Patent Application Kokai No. 125664/1981 is one in which each of the grains is irradiated one at a time by a visible ray and the amount of reflected light and the amount of transmitted light are measured thereby to make the determination as to whether the given grain is a complete grain, a milk white grain, a greenish grain, a brownish grain or a dead grain. Patent Application Kokai No. 153249/1982 discloses a method in which each of the grains is irradiated by a ray of a predetermined wave length and the factor of transmission is measured thereby to make the determination as to whether the given grain is an inferior one by the comparison of the transmission factor with the predetermined value of threshold. Patent Application Kokai No. 150141/1987 discloses a method in which each of the brown rice grains is irradiated by a ray and the amount of diffused transmitted light, the amount of diffused reflected light, the amount of light having predetermined two wave lengths in the diffused reflected light and the amount of transmitted light at two positions of each of the grains are detected thereby to make the determination as to whether the given grain is a complete grain, a milk white grain, an immature greenish grain, a cracked grain, a damaged grain, a discolored grain, and a greenish or whitish dead grain. The determination is enabled by the calculation of the ratios of the amount of diffused transmitted light and the amount of diffused reflected light and the ratios of the amounts of light of the optional two wave lengths among the diffused reflected light and the amounts of transmitted light at two positions of each of the grains and by the processing of the ratio value of the respective amounts of light for making the determination.
With the conventional apparatus or methods as described above, it was not possible to achieve an accurate grading determination of grains because the matters subject for detection as reference for the determination are of a single datum covering only the amount of reflected light and the amount of transmitted light. That is, even when the given grain is a complete grain (regular grain), the amount of reflected light and the amount of transmitted light can vary due to different factors such as rice plant varieties, production districts and cultivating methods and such grain may not necessarily be evaluated as a complete grain and this makes it difficult to achieve the constant and high accuracy for the grading determination. As an example, a frequency distribution of foreign particles and various grades of grains such as discolored grains, chalky grains is shown in FIG. 11 from which it is understood that, since the curves for respective grains overlap one another in the direction of X axis (brightness=amount of reflected light), it is not possible to achieve an accurate determination of the respective grades when the border lines among them are positioned at such overlapped regions.
It is more desirable that the measuring of the transmitted light and the reflected light takes place at the same position in a means on which rice gains flow. If the measuring is made at different positions respectively for the transmitted light and for the reflected light, it is possible for the grain to develop changes between the two positions and such changes adversely affect the evaluation of the grade of rice grains.
In order to overcome the problems as explained above, the present invention provides an apparatus for evaluating the grade of rice grains with which it is possible to perform an accurate determination of grades of rice grains.